Hydrocarbons and other fluids are often contained within subterranean formations at elevated pressures. Wells drilled into these formations allow the elevated pressure within the formation to force the fluids to the surface. However, in low pressure formations, or when the formation pressure has diminished, the formation pressure may be insufficient to force fluids to the surface. In these cases, a positive displacement pump, such as a piston pump, can be installed to provide the required pressure to produce the fluids.
The function of pumping systems in gas wells is to produce fluid (generally water) that enters the well bore naturally with the gas. This is typically necessary only on low flow rate gas wells. In high flow rate gas wells, the velocity of the gas is usually sufficient that it carries the water to the surface. In low flow rate gas wells, the water accumulates in the well bore and restricts the flow of gas. By pumping out the water, the pump allows the well to flow at a higher gas rate, and this additional produced gas, which eventually is related to additional revenue, pays for the pumping unit.
Positive displacement pumps operate at a fixed volume rate. For a given pump geometry (stroke, diameter), the speed of the pump must be changed in order to change the flow rate of the pump.